CN105236951A - Heat insulator - Google Patents

Abstract

To provide a light-weight heat insulating material including a porous sintered body in which an increase in thermal conductivity is suppressed, that is, a light-weight heat insulating material that can improve workability during construction while maintaining heat insulating properties at high temperatures. In one aspect of the heat insulating material of the present invention, it includes a porous sintered body with a porosity of 70 vol% or more and less than 91 vol%, and pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 10 vol% or more and 70 vol% or less of the total pore volume, And pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for 5 vol% or more and 30 vol% or less of the total pore volume, and the porous sintered body is a fiber formed from MgAl ₂ O ₄ (spinel) raw materials and inorganic materials The formed sintered body has a thermal conductivity of 0.40 W/(m·K) or less at 1000° C. to 1500° C., and a weight ratio of Si to Mg in the porous sintered body is 0.15 or less.

Description

insulation material

technical field

The present invention relates to a heat insulating material, particularly a heat insulating material comprising a porous sintered body of MgAl ₂ O ₄ and having excellent heat insulating properties in a temperature range of 1000° C. or higher. That is, the present invention relates to a heat insulating material including a spinel porous sintered body.

Background technique

A ceramic porous body of magnesia spinel is valued as a material of a heat insulating material that suppresses an increase in thermal conductivity in a high temperature range of 1000° C. or higher and is also excellent in heat resistance.

In Japanese Patent Laid-Open No. 2012-229139 (Patent Document 1) and Japanese Patent Laid-Open No. 2013-209278 (Patent Document 2), it is disclosed that a spinel ceramic porous body having a predetermined pore size distribution can suppress conduction Heat conduction and radiant heat conduction, and thus can be used as a heat insulating material excellent in heat resistance even at high temperatures of 1000° C. or higher.

However, the spinel ceramic porous bodies described in the above-mentioned Patent Documents 1 and 2 have low thermal conductivity and good heat resistance at 1000°C or higher, which is higher than before, but their strength is high due to their high porosity. insufficient.

In order to improve the strength, the method of reducing the porosity and increasing the bulk specific gravity (bulk specific gravity) is generally adopted. However, in the heat insulating materials described in Patent Documents 1 and 2, thermal conductivity increases and bulk specific gravity increases only by lowering the porosity. Therefore, it is not enough to satisfy the requirements of a light and easy-to-handle heat insulating material with low thermal conductivity. requirements.

On the other hand, in recent years, there has been a tendency to demand a light-weight, high-strength heat insulating material that can suppress an increase in thermal conductivity even in a high temperature range of 1000° C. or higher.

As an example of a lightweight, high-strength heat insulating material, a composite material including a heat insulating material formed of a porous body and a fiber-containing material is known.

For example, in Japanese Patent Application Laid-Open No. 10-226582 (Patent Document 3), a multilayer heat insulating material excellent in mechanical properties and heat resistance that can be used in a temperature range exceeding about 1500°C and can be produced by a simple method , which records such an invention: it is composed of the following three layers (A), (B) and (C); , (B) the middle layer, (C) a thermal insulation layer containing 15-35% by weight of mullite fibers and 65-85% by weight of silica fibers, and has a glassy boron compound that fixes the entanglement points of the fibers, in the form of Multi-layer thermal insulation material with three-dimensional network structure.

In the invention described in Patent Document 3, when attempting to apply the spinel ceramic porous body described in Patent Documents 1 and 2, in order to ensure high strength while maintaining excellent heat insulation at high temperature, the The weight becomes heavy, and the ease of handling, that is, the operability at the time of construction, is not sufficient. In addition, as the weight increases, the specific heat of volume increases, and the amount of heat required to raise the temperature of the heat insulating material may increase.

Contents of the invention

In order to solve the above-mentioned technical problems, the present inventors found: a heat insulating material comprising a MgAl ₂ O ₄ ceramic sintered body, the porosity of which is 85 vol% or more and less than 91 vol%, and the pore diameter is 0.8 μm or more and low The pores with a diameter of 10 μm account for more than 10 vol% and less than 40 vol% of the total pore volume, and the pores with a diameter of 0.01 μm or more and less than 0.8 μm account for more than 5 vol% and less than 10 vol% of the total pore volume, and the heat insulating material is maintained at It has excellent heat insulating properties such as suppressing an increase in thermal conductivity even at a high temperature of 1000° C. or higher, and is also excellent in light weight, so it was previously filed as Japanese Patent Application No. 2014-249484.

Then, after further intensive research, it was found that if Si is contained in the MgAl ₂ O ₄ ceramic sintered body, the shrinkage increases during high-temperature use (reheating shrinkage increases), low thermal conductivity cannot be obtained, and good heat resistance cannot be obtained. , thus thinking of the present invention. In addition, the Si exists as an impurity in the MgAl ₂ O ₄ based ceramic sintered body, or is contained in a ceramic reinforcing material that strengthens the ceramic sintered body.

In view of the above-mentioned technical problems, an object of the present invention is to provide a heat insulating material that can suppress an increase in thermal conductivity even at a high temperature of 1000° C. or higher while maintaining excellent heat insulating properties and being excellent in lightness. That is, an object of the present invention is to provide a heat insulating material (composite heat insulating material) that is excellent in heat insulating properties at high temperatures, is lightweight, has a small volume specific heat, and has excellent handleability.

The heat insulating material according to one aspect of the present invention is characterized in that it includes a porous sintered body with a porosity of 70 vol% or more and less than 91 vol%, and pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 10 vol% or more of the total pore volume. And 70vol% or less, and pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for 5 vol% or more and 30 vol% or less of the total pore volume, the porous sintered body is made of MgAl ₂ O ₄ (spinel) raw material and A sintered body made of fibers made of an inorganic material, having a thermal conductivity of 0.40 W/(m·K) or less at 1000°C to 1500°C, and a weight ratio of Si to Mg in the porous sintered body of 0.15 the following.

The weight ratio of Si to Mg in the porous sintered body is preferably 0.0001 or less.

The heat insulating material preferably includes a MgAl ₂ O ₄ ceramic sintered body, its porosity is 85 vol% or more and less than 91 vol%, and pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 10 vol% or more of the total pore volume and 40vol% or less, and pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for 5 vol% or more and 10 vol% or less of the total pore volume.

In addition, the heat insulating material preferably includes a MgAl ₂ O ₄ ceramic porous body, the porosity of which is 70 vol% or more and less than 85 vol%, and the pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 40 vol% of the total pore volume. More than 70 vol%, and pores with a diameter of 0.01 μm or more and less than 0.8 μm account for 10 vol% or more and 30 vol% or less of the total pore volume.

In this way, in the heat insulating material according to the present invention, since the weight ratio of Si to Mg in the sintered body is 0.15 or less, reheating shrinkage at 1600° C. is small, and a predetermined pore size distribution can be maintained. That is, a predetermined pore diameter distribution can be maintained, and low thermal conductivity and good heat resistance can be obtained. Furthermore, if the weight ratio of Si to Mg in the sintered body is 0.0001 or less, reheat shrinkage at 1700° C. can be reduced.

The inorganic material is preferably a ceramic reinforcement material. And the ceramic reinforcing material is more preferably ceramic fiber.

Incidentally, the added amount of the ceramic reinforcing material is 0.5 wt % to less than 60 wt %, more preferably 5 wt % to 50 wt %, in terms of weight ratio to the solid content other than the ceramic reinforcing material. By adding a predetermined amount of a ceramic reinforcing material with a silica content of 5 wt% or less, a heat insulating material excellent in heat resistance and heat insulating properties can be obtained.

It should be noted that the lower the thermal conductivity of the thermal insulation material at high temperature, the more excellent the thermal insulation effect can be obtained, so the thermal conductivity at 1000°C to 1500°C is 0.40W/(m·K) or lower. In addition, regarding reheat shrinkage in the heat insulating material, the shrinkage when held at 1600°C for 12 hours is preferably 2% or less, and for the heat insulating material in which the weight ratio of Si to Mg in the sintered body is 0.0001 or less, it is preferably Shrinkage at 1700°C for 12 hours is 2% or less.

The heat insulating material according to the present invention is characterized in that it includes a porous sintered body with a porosity of 70% or more, and the porous sintered body includes a spinel sintered body and at least one side of the spinel sintered body. A fibrous layer on the surface, wherein said spinel sintered body is formed of MgAl ₂ O ₄ (spinel) raw material, said fibrous layer is formed of fibers formed from an inorganic material, pores with a pore diameter of more than 1000 μm are formed in said porous The total pores of the sintered body are less than 10vol%, the pores with a diameter of 0.8 μm or more and less than 10 μm account for more than 50vol% and less than 80vol% of the pores with a diameter of 1000 μm or less, and the pores with a diameter of 0.01 μm or more and less than 0.8 μm are in the Pores with a pore diameter of 1000 μm or less account for 10 vol% or more and 30 vol% or less, the silica component in the fibers in the fibrous layer is 55 wt% or less, and the thermal conductivity at 1000°C or more and 1500°C or less is 0.40 W/(m?K) below.

That is, the heat insulating material according to the present invention is characterized by comprising a porous sintered body composed of chemical formula XAl ₂ O ₄ and a fibrous layer formed on at least one surface of the porous sintered body. Spinel, X in the chemical formula is any type of Zn, Fe, Mg, Ni and Mn, specifically, the spinel composed of chemical formula XAl ₂ O ₄ is MgAl ₂ O ₄ , the fiber The mass layer contains an aggregate of fibers formed of inorganic materials, and in the porous sintered body, the porosity is 70% or more, and the pores with a pore diameter exceeding 1000 μm are 10vol% or less of the total pores in the porous sintered body, and the pore diameter is 0.01 μm The pores above and below 0.8 μm account for more than 10 vol% and less than 30 vol% of the pores with a pore diameter of 1000 μm or less, and the pores with a pore diameter of 0.8 μm or more and less than 10 μm account for more than 50 vol% and 80 vol% of the pores with a pore diameter of 1000 μm or less Hereinafter, the silica component in the fibers in the fibrous layer is 55 wt % or less, and the thermal conductivity at 1000° C. to 1500° C. is 0.40 W/(m·K) or less.

With this configuration, it is possible to obtain a heat insulating material that is excellent in heat insulating properties at high temperatures, is lightweight, has a small volumetric specific heat, and is excellent in handleability.

A heat insulating material according to an aspect of the present invention is characterized in that it includes a porous sintered body with a porosity of 85 vol% or more and less than 91 vol%, and the porous sintered body is made of MgAl ₂ O ₄ (spinel) raw material and ceramic fiber Formation (including ceramic fibers in MgAl ₂ O ₄ (spinel)), pores with a pore size of 0.8 μm or more and less than 10 μm account for 10 vol% or more and 40 vol% of the total pore volume, and the pore size is 0.01 μm or more and less than The pores of 0.8 μm account for more than 5vol% and less than 10vol% of the total pore volume, the thermal conductivity at 1000°C to 1500°C is less than 0.40W/(m?K), and the bulk specific gravity is less than 0.6.

With this configuration, a lightweight heat insulating material can be provided while maintaining low thermal conductivity.

In addition, since the more suppressed the increase in thermal conductivity at high temperature, the more excellent heat insulation effect can be obtained in the high temperature range, so it is preferable that the thermal conductivity at 1000°C to 1500°C is not more than 20°C to 1000°C 1.5 times the thermal conductivity below.

In addition, the heat insulating material according to another aspect of the present invention is characterized in that it includes a porous sintered body with a porosity of 70 vol% or more and less than 85 vol%, and the porous sintered body is made of MgAl ₂ O ₄ (spinel) raw material and Formation of ceramic fibers (ceramic fibers are contained in MgAl ₂ O ₄ (spinel)), pores with a pore diameter of 0.8 μm or more and less than 10 μm account for more than 40 vol% and less than 70 vol% of the total pore volume, and pore diameters of 0.01 μm or more And the pores below 0.8μm account for more than 10vol% and less than 30vol% of the total pore volume, and the thermal conductivity above 1000°C and below 1500°C does not exceed the thermal conductivity above 20°C and below 1000°C 1.5 times.

By having this configuration, it is possible to provide a heat insulating material in which an increase in thermal conductivity in a high temperature range is further suppressed while being lightweight.

The heat insulating material has a thermal conductivity lower than 0.40 W/(m·K) at temperatures above 1000°C and below 1500°C. Preferably it is 0.35W/(m·K) or less.

In addition, since the more suppressed the increase in thermal conductivity at high temperature, the more excellent heat insulation effect can be obtained in the high temperature range, so it is preferable that the thermal conductivity at 1000°C to 1500°C is not more than 20°C to 1000°C 1.2 times the thermal conductivity below.

The heat insulating material related to the present invention is a heat insulating material that can suppress an increase in thermal conductivity at a high temperature of 1000° C. or higher, maintain excellent heat insulating properties, and is light and easy to handle. Furthermore, by appropriately controlling the pore volume of different pore diameters, thermal conductivity and light weight can be optimized according to the application, which is more preferable.

According to the present invention, it is possible to provide a heat insulating material that is excellent in heat insulating properties at high temperatures, is lightweight, has a small volume specific heat, and is excellent in handleability.

Description of drawings

FIG. 1 is a graph showing the pore diameter distribution of each porous sintered body measured by a mercury porosimeter in Examples 1 to 3 and Reference Example 1 according to the present invention.

2 is a graph showing the pore size distribution of each porous sintered body measured by a mercury porosimeter in Example 1, Example 1A, Example 2, and Example 2A according to the present invention.

3 is a graph showing the relationship between temperature and thermal conductivity for each porous sintered body or heat-insulating brick in Examples and Comparative Examples according to one aspect of the present invention.

Fig. 4 is a graph showing the relationship between temperature and thermal conductivity for each porous sintered body or heat-insulating brick according to Examples and Comparative Examples according to another aspect of the present invention.

5 is a graph showing the pore size distribution of each porous sintered body measured by a mercury porosimeter in Examples and Reference Examples according to the present invention.

detailed description

The heat insulating material involved in the embodiment of the present invention will be described below.

The heat insulating material according to one aspect of the present invention includes a porous sintered body with a porosity of 70 vol% or more and less than 91 vol%, and pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 10 vol% or more and 70 vol% of the total pore volume Below, and pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for ₅ vol% or more and 30 vol% or less of the total pore volume _. The thermal conductivity of the sintered body formed of the fibers is 0.40 W/(m·K) or less at 1000° C. to 1500° C., and the weight ratio of Si to Mg in the porous sintered body is 0.15 or less.

The weight ratio of Si to Mg in the porous sintered body is preferably 0.0001 or less.

The heat insulating material involved in a preferred aspect of the present invention includes a MgAl ₂ O ₄ ceramic sintered body, the porosity of which is 85 vol% or more and less than 91 vol%, and the pores with a pore diameter of 0.8 μm or more and less than 10 μm account for the total pore volume 10 vol% to 40 vol%, and pores with a pore diameter of 0.01 μm to 0.8 μm account for 5 vol% to 10 vol% of the total pore volume.

The heat insulating material related to another preferred aspect of the present invention includes a MgAl ₂ O ₄ ceramic porous body containing a reinforcing material, including a porous sintered body with a porosity of 70 vol% or more and less than 85 vol% and a pore diameter of 0.8 μm or more And the pores below 10 μm account for more than 40 vol% and less than 70 vol% of the total pore volume, and the pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for more than 10 vol% and less than 30 vol% of the total pore volume.

The heat insulating material involved in the present invention is made of spinel MgAl ₂ O ₄ (magnesia spinel). The spinel porous sintered body has little variation in the shape and size of pores due to grain growth at high temperature and bonding of grain boundaries, and can maintain the effect of suppressing variation in thermal conductivity for a long period of time.

In particular, MgAl ₂ O ₄ has an isotropic crystal structure with high structural stability in a high temperature range of 1000° C. or higher, and therefore hardly undergoes specific grain growth or shrinkage even when exposed to high temperatures. Therefore, MgAl ₂ O ₄ is preferable as a heat insulating material used at high temperatures because it can maintain the specific pore structure that is the characteristic of the present invention. It should be noted that the chemical composition and spinel structure can be measured and identified by, for example, powder X-ray diffraction.

Moreover, the porosity of the porous sintered body in one aspect of this invention is set to 70 vol% or more and less than 91 vol%. When the porosity is lower than 70 vol%, the proportion of the base material formed by MgAl ₂ O ₄ in the porous sintered body is high, the conduction heat transfer increases, and it is difficult to make the thermal conductivity small enough. On the other hand, when the porosity is 91 vol% or more, the proportion of the base material portion made of MgAl ₂ O ₄ in the porous sintered body is absolutely low, so it becomes extremely fragile and cannot obtain sufficient strength. .

The said porosity is computed by JISR2614 "The measuring method of the specific gravity and true porosity of a refractory heat insulating brick".

As a preferred aspect of the porous sintered body, when the porosity is 85 vol% or more and less than 91 vol%, the pore structure is such that pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 10 vol% or more and 40 vol% of the total pore volume. % or less, pores with a pore diameter of 0.01 μm or more and less than 0.8 μm (hereinafter also referred to as “micro pores”) account for 5 vol% or more and 10 vol% or less in the total pore volume.

By adopting such a pore structure, it is possible to maintain pores with a pore diameter of 0.01 μm or more to less than 0.8 μm necessary for suppressing conduction heat transfer and pores with a pore diameter of 0.8 μm or more to less than 10 μm necessary for suppressing radiation heat transfer, and to make the pores The rate is above 85vol%. By having pores with a pore diameter of 0.01 μm or more and less than 0.8 μm, conduction heat transfer can be suppressed by phonon scattering. By having pores with a diameter of 0.8 μm or more and less than 10 μm, radiation heat transfer can be suppressed by scattering of infrared rays.

When the ratio of the microscopic pores to the total pore volume is less than 5 vol%, the number of pores per unit volume is small, and the effect of suppressing conduction and heat transfer may become insufficient. On the other hand, if the ratio exceeds 10 vol%, it may be difficult to obtain a porosity of 85 vol% or more.

Here, the porous sintered body does not matter even if it has a pore size distribution peak in a range of more than 10 μm in pore size.

In another preferred version of the porous sintered body, when the porous sintered body has a porosity of 70 vol% or more and less than 85 vol%, pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 40 vol% of the total pore volume More than and less than 70 vol%, and pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for more than 10 vol% and less than 30 vol% of the total pore volume.

If the pores with a pore diameter of 0.8 μm or more and less than 10 μm are less than 40 vol% of the total pore volume, the conduction heat transfer suppression effect may be small, and if it is more than 70 vol%, it may be difficult to obtain a porosity of 70 vol% or more. If pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for less than 10 vol% of the total pore volume, a porosity of 70 vol% or more and the effect of suppressing radiation heat transfer due to infrared scattering may not be obtained.

The pore size distribution in the porous sintered body can be measured in accordance with JIS R1655 "Test method for pore size distribution of molded body of fine ceramics by mercury porosimetry". In addition, bulk specific gravity (bulk density) can be measured by JISR2614 "the specific gravity of a refractory heat insulating brick and the measuring method of true porosity."

It should be noted that in the preferred solution of the present invention, as long as the pores with a pore diameter of 0.8 μm or more and less than 10 μm account for more than 10 vol% and less than 40 vol% of the total pore volume, and the pores with a pore diameter of 0.01 μm or more and less than 0.8 μm are in the The total pore volume accounts for more than 5 vol% and less than 10 vol%, or the pores with a pore diameter of 0.8 μm or more and less than 10 μm account for more than 40 vol% and less than 70 vol% of the total pore volume, and the pore diameter is more than 0.01 μm and less than 0.8 μm If the pores account for more than 10 vol% and less than 30 vol% of the total pore volume, each scheme can also include pores of 10 μm or more.

In addition, in the heat insulating material according to the present invention, the weight ratio of Si to Mg is 0.15 or less.

In this way, by setting the weight ratio of Si to Mg to be 0.15 or less, reheat shrinkage is small (shrinkage during use at high temperature is suppressed), and a predetermined pore size distribution can be maintained. That is, a predetermined pore size distribution can be maintained, and low thermal conductivity and good heat resistance can be obtained. Specifically, the reheat shrinkage of the heat insulating material according to the present invention is preferably 2% or less when kept at 1600° C. for 12 hours. In addition, for a heat insulating material having a weight ratio of Si to Mg of 0.0001 or less, the shrinkage when kept at 1700° C. for 12 hours is preferably 2% or less.

In addition, the porous sintered body according to the present invention preferably contains ceramic fibers as the ceramic reinforcing material. When the ceramic fibers are included in the porous sintered body, the porosity of the entire porous sintered body can be increased, and the bulk specific gravity can be reduced, so that the weight can be reduced. Furthermore, compared with the case where the porosity is only increased without adding fibers, the strength can also be improved.

As the ceramic fibers, well-known materials used for heat insulating materials can be widely used, and examples thereof include alumina, zirconia, alumina-silica, and the like. However, ceramic fibers that are oxidatively decomposed in a high-temperature atmosphere, or oxidized in a high-temperature atmosphere, such as silicon carbide, are not necessarily preferable (less preferable).

The shape of the ceramic fiber is also not particularly limited. For example, short fibers having an average diameter of 3 to 10 μm and an average length of 0.2 to 100 mm, fiber bundles obtained by bundling hundreds to thousands of such short fibers, or continuous long fibers may be included. However, from the viewpoint of maintaining the porosity within the range of the present invention, the form in which the aforementioned short fibers are dispersed is preferable.

The addition rate of ceramic fibers is not particularly limited, but if it is too small, the effect of reducing the bulk specific gravity may hardly be obtained. In addition, if it is too large, the proportion of pores with a pore diameter of 0.01 μm or more to less than 0.8 μm and pores with a pore diameter of 0.8 μm or more and less than 10 μm in the whole will decrease, and thus the suppression of the increase in thermal conductivity described later may not be sufficiently obtained. Effect.

In addition, the content of silica in the ceramic fibers is preferably 5 wt % or less, and is preferably added in an amount of 0.5 wt % or more and less than 60 wt % of the sintered body. In this way, the content of silicon dioxide in the ceramic fiber is set to 5 wt % or less, and it is added in an amount of 0.5 wt % or more and less than 60 wt % of the sintered body, thereby making it possible to make the silica in the sintered body The weight ratio of Si to Mg is 0.15 or less.

That is, by adding a ceramic reinforcing material having a silica content of 5 wt% or less in an amount of 0.5 wt% to less than 60 wt% of the sintered body, a heat insulating material excellent in heat resistance and heat insulation can be obtained.

In addition, the distribution of ceramic fibers in MgAl ₂ O ₄ can also be timely adjusted according to the requirements of the designed thermal insulation material. As an example, if the density of the fiber is made high in the surface layer and low in the center, since the surface layer has high strength, it can be made into a heat insulating material that is difficult to deform.

As shown in the above-mentioned preferred solution, ceramic fibers are contained in MgAl ₂ O ₄ , the porosity is more than 85vol% and less than 91vol%, and the pores with a pore diameter of 0.8μm or more and less than 10μm account for more than 10vol% of the total pore volume And 40vol% or less, pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for 5 vol% or more and 10 vol% or less of the total pore volume. By including ceramic fibers in such a pore form, it is possible to achieve weight reduction without reducing strength , which can reduce the bulk specific gravity.

Furthermore, by setting the content of silica in the ceramic fiber to 5 wt % or less, and adding it in an amount of 0.5 wt % or more to less than 60 wt % of the sintered body, it is possible to make the relative When the weight ratio of Mg to Si is 0.15 or less, reheating shrinkage is small (shrinkage is suppressed during use at high temperature), and a predetermined pore size distribution can be maintained. As a result, a predetermined pore diameter distribution can be maintained, and low thermal conductivity and good heat resistance can be obtained.

In addition, regarding the thermal conductivity of the heat insulating material, specifically, it is preferable that the thermal conductivity between 1000°C and 1500°C is not more than 1.5 times the thermal conductivity between 20°C and below 1000°C.

The heat insulating material whose thermal conductivity is suppressed in the high temperature range can maintain the same heat insulating effect as that in the low temperature range below 1000°C even in the high temperature range of 1000°C or higher.

The heat insulating material has a thermal conductivity of 0.40 W/(m·K) or less in a high temperature range of 1000°C to 1500°C. In this way, the heat insulating material whose thermal conductivity is suppressed and not increased even in the high temperature range of 1000° C. or higher has little variation in the heat insulating effect when used in the high temperature range.

It should be noted that the method of manufacturing the heat insulating material involved in the present invention is not particularly limited, and a known method of manufacturing a porous sintered body can be applied. For example, the formation and adjustment of the pore structure can be performed by adding a pore-forming material, a foaming agent, and the like.

In addition, the heat insulating material according to the present invention can have various modifications as long as there is no adverse effect such as significantly deteriorating the heat insulating properties. For example, fibers made of various materials may also be added. In addition, fine particles may be further added. Alternatively, a fiber-free region may be partially set. Furthermore, various films may be provided on the surface layer of the heat insulating material according to the present invention to further improve heat resistance.

The heat insulating material related to the present invention includes a porous sintered body having a porosity of 70% or more, the porous sintered body including a spinel sintered body and fibers existing on at least one surface of the spinel sintered body wherein the spinel sintered body is formed of MgAl ₂ O ₄ (spinel) raw material, the fibrous layer is formed of fibers formed of inorganic materials, and pores with a pore diameter exceeding 1000 μm are in the porous sintered body The total pores are less than 10vol%, the pores with a diameter of 0.8 μm or more and less than 10 μm account for more than 50vol% and less than 80vol% of the pores with a diameter of less than 1000 μm, and the pores with a diameter of 0.01 μm or more and less than 0.8 μm are less than 1000 μm 10vol% to 30vol% of the pores, the silica component in the fibers in the fibrous layer is 55wt% or less, and the thermal conductivity at 1000°C to 1500°C is 0.40W/( m?K) below.

In other words, the heat insulating material involved in the present invention includes a porous sintered body and a fibrous layer formed on at least one surface of the porous sintered body, wherein the porous sintered body is spinel composed of the chemical _{formula XAl2O4} , In the chemical formula, X is any one of Zn, Fe, Mg, Ni and Mn, that is, X is Mg, the fibrous layer includes an aggregate of fibers formed of inorganic materials, and in the porous sintered body, the porosity is More than 70% of the pores with a diameter of more than 1000 μm account for 10 vol% or less of the total pores in the porous sintered body, and pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for 10 vol% or more and 30 vol% or less of the pores with a pore diameter of 1000 μm or less The pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 50 vol% or more and 80% or less of the pores with a pore diameter of 1000 μm or less, and the silica component in the fibers in the fibrous layer is 55 wt% or less, The thermal conductivity at 1000° C. to 1500° C. is 0.40 W/(m·K) or less.

The present invention includes a porous sintered body formed of a spinel of the chemical formula XAl ₂ O ₄ (X in the chemical formula is any one of Zn, Fe, Mg, Ni, and Mn, ie, Mg).

The spinel composed of the chemical formula XAl ₂ O ₄ , specifically the magnesia spinel in which X is Mg, has small changes in the shape and size of pores generated by grain growth at high temperature and the bonding of grain boundaries. , the effect of suppressing fluctuations in thermal conductivity can be maintained for a long period of time, so it is preferably used at high temperatures. It should be noted that the chemical composition and spinel structure can be measured and identified by, for example, powder X-ray diffraction.

In the porous sintered body, the porosity is 70% or more, the pores with a diameter of more than 1000 μm are 10 vol% or less of the total pores of the porous sintered body, and the pores with a diameter of 0.01 μm or more and less than 0.8 μm are pores with a diameter of 1000 μm or less 10 vol% to 30 vol%, pores with a pore diameter of 0.8 μm to 10 μm account for 50 vol% to 80 vol% of the pores with a pore diameter of 1000 μm or less.

The porosity can be calculated according to JIS R2614 "Measuring method of specific gravity and true porosity of refractory and heat-insulating bricks". Furthermore, the pore volume ratio can be obtained from the pore size distribution which can be measured in accordance with JIS R1655 "Test method for pore size distribution of molded articles of fine ceramics by mercury pressure method".

When the porosity of the porous sintered body is less than 70%, the proportion of solids increases, so conduction heat transfer increases, and thermal conductivity may increase. In addition, if the porosity is too high, the strength will decrease remarkably, so the upper limit of the porosity is preferably 88%.

In a porous sintered body, if there are too many so-called giant pores with a pore diameter of more than 1000 μm, the temperature dependence of thermal conductivity may increase. Therefore, if the pores with a pore diameter of more than 1000 μm account for 10 vol% or less of the total pores, the This influence is suppressed to a practically non-problematic level.

Pores with a pore diameter of 0.01 μm or more and less than 0.8 μm, the so-called micro pores account for 10 vol% or more and 30 vol% or less of the pores with a pore diameter of 1000 μm or less, so that the number of pores per unit volume can be increased, and the phonons at the grain boundary The amount of scattering increases, thereby obtaining the effect of suppressing conduction heat transfer.

If the micropores are less than 10 vol%, the number of grain boundaries per unit volume will decrease, and the effect of suppressing conduction and heat transfer will be insufficient. On the other hand, if the micropores exceed 30 vol%, it will be difficult to increase the porosity to 70% or more, resulting in increased thermal conductivity.

In the porous sintered body according to the present invention, the pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 50 vol% or more and 80 vol% or less of the pores with a pore diameter of 1000 μm or less. The fine pores are within the scope of the present invention, and an appropriate amount of pores of 0.8 μm or more and 10 μm or less suitable for suppressing radiation heat transfer exists, thereby effectively suppressing an increase in thermal conductivity at high temperatures as a whole.

The above pore volume ratio for each pore diameter is determined in consideration of the formation of a fibrous layer on the surface. Therefore, it is possible to suppress a significant decrease in thermal insulation properties at high temperatures due to an increase in radiation heat transfer due to the provision of the fibrous layer, and it can be said that the original characteristics of the porous sintered body of the present invention can be maintained.

In the present invention, the silica component in the fibers of the fibrous layer is 55% by weight or less.

The fibrous layer effectively makes up for the weakness of the porous sintered body of the present invention, that is, lack of toughness and light weight, without impairing the thermal insulation properties at high temperatures.

Although the porous sintered body in the present invention has excellent thermal insulation properties at high temperatures, for example, if it is made into a plate shape, it will be difficult to carry out during transportation, stacking operations on the inner surface of the furnace body, etc., and all other operations. , there may be defects such as cracking, chipping, breaking or other damage.

As a countermeasure against these disadvantages, there is a method of improving the strength of the porous sintered body itself. In this case, the increase in bulk density may impair lightness, and workability at the time of construction may deteriorate. In the present invention, workability during construction is referred to as workability for convenience.

In addition, since the above method is aimed at improving the strength of the so-called bulk body, for example, in a plate-shaped material, bending occurs due to its own weight, so a strong tensile stress is generated in the surface layer of the porous sintered body, and cracks are generated in the surface layer. etc., the porous sintered body which is a brittle material is easily damaged.

Therefore, a method of forming a layer on the surface layer of the porous sintered body for reinforcement is conceivable. In this method, as long as the thickness of the layer is not too thick, the risk of breakage as described above can be reduced while suppressing an increase in bulk density as a whole. In addition, it also has the function of protecting the surface layer, so it can effectively prevent the occurrence of scratches and chipping.

However, the porous sintered body involved in the present invention exhibits the effect of excellent thermal insulation at high temperatures due to its unique pore diameter and pore volume ratio, but forming a layer only on its surface may damage the thermal insulation properties at high temperatures. Under the effect of thermal insulation.

Therefore, in the present invention, while optimizing the pore volume ratio of the porous sintered body, as the layer formed on the surface layer, by using a material containing particularly high-strength fibers, it is possible to obtain a high-temperature performance. Thermal insulation material with thermal insulation, light weight, operability, and high toughness.

Here, being formed on at least one surface of the porous sintered body means that the entire surface of the porous sintered body is covered with a fibrous layer and is not an essential condition. Depending on the shape and method of use of the heat insulating material, it is difficult to cover the entire surface, but there is no particular limitation as long as the fibrous layer is provided within the range in which the effects of the present invention can be obtained.

If it is a plate shape, it may be a form in which at least one main surface is covered with a fibrous layer. In the case of a block, only the operation surface may be covered with a fibrous layer.

As the fibers made of inorganic materials, known inorganic materials suitable for heat insulating materials and refractories can be widely used, and are not particularly limited. For example, alumina, mullite, zirconia, etc. are mentioned.

In addition, the form of the fiber is not particularly limited, and can be appropriately selected according to the purpose of use and application. Examples thereof include a material obtained by dispersing so-called short fibers in a matrix, a sheet or fabric of long fibers, a composite of short fibers and long fibers, and the like.

The fibrous layer including an aggregate of fibers made of an inorganic material has the fibers made of an inorganic material as an essential component, and may also contain other materials as an appropriate component. For example, if a layer cannot be formed with a single fiber component, an appropriate inorganic material can be selected as the matrix. In addition, a film for improving heat resistance and corrosion resistance may be further formed on the surface of the fibrous layer.

As described above, although the form of the fibrous layer is not particularly limited in the present invention, the silica component in the fibers in the fibrous layer is 55 wt % or less. This is because when the silica component exceeds 55 wt%, the reaction between the spinel of the porous sintered body and the silica in the fibers increases to an unnegligible level, and as a result, the risk of detachment of the fibrous layer increases.

It should be noted that most of known fibers made of inorganic materials and suitable for heat insulating materials or refractories contain silica components. Therefore, in the present invention, the ratio of the silica component contained in the fiber is limited in order to avoid the above-mentioned inconvenience caused by too much silica component.

Although there is no particular limitation on the thickness of the fibrous layer, for example, in the case of a plate-shaped heat insulating material, if the ratio of the fibrous layer to the overall thickness is large, the heat insulation at high temperature will be impaired. , Therefore, timely design according to the balance with operability.

In addition, materials other than the porous sintered body and the fibrous layer may be further contained within a range not impairing the effect of the present invention. For example, fibers or the like may be added to the porous sintered body as a reinforcing material. The reinforcing material and the porous sintered body involved in the present invention may be the same material or different materials. In addition, a known pore-forming material may be added to the above.

It should be noted that if the heat insulating material involved in the present invention has a thermal conductivity lower than 0.4W/(m?K) in the temperature range of 1000°C to 1500°C, it can provide thermal insulation caused by the fibrous layer. It can be said that it is more preferable to suppress the influence of property reduction to a minimum.

The heat insulating material according to one aspect of the present invention is characterized in that it includes a porous sintered body with a porosity of 85 vol% or more and less than 91 vol%, and pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 10 vol% or more of the total pore volume. And 40vol% or less, and pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for 5 vol% or more and 10 vol% or less of the total pore volume. The porous sintered body is made of MgAl ₂ O ₄ (spinel) raw materials and ceramic fibers Formed (including ceramic fibers in MgAl ₂ O ₄ ), the thermal conductivity at 1000°C to 1500°C is 0.40W/(m·K) or less, and the bulk specific gravity is 0.6 or less.

The material of the porous sintered body in the present invention is spinel MgAl ₂ O ₄ (magnesia spinel). In the spinel porous sintered body, the variation in shape and size of pores due to grain growth at high temperature and bonding of grain boundaries is small, and the effect of suppressing variation in thermal conductivity can be maintained for a long time.

In particular, MgAl ₂ O ₄ has high structural stability in the high temperature range of 1000°C or higher, and has an isotropic crystal structure, so even when exposed to high temperatures, specific grain growth and shrinkage hardly occur .

Therefore, since MgAl ₂ O ₄ can maintain the specific pore structure characteristic of the present invention, it is preferable as a heat insulating material used at high temperatures. It should be noted that the chemical composition and spinel structure can be measured and identified by, for example, powder X-ray diffraction.

In addition, the porous sintered body according to the present invention contains ceramic fibers. When ceramic fibers are contained in MgAl ₂ O ₄ , the porosity of the entire porous sintered body can be increased, and the bulk specific gravity can be reduced, so that weight can be reduced. Furthermore, compared with the case where only the porosity is increased without adding fibers, the strength can also be improved.

As the ceramic fiber, well-known materials used for heat insulating materials can be widely applied, and examples thereof include alumina, zirconia, mullite, and the like. However, materials that cannot be used due to oxidative decomposition in a high-temperature atmosphere, such as silicon carbide, are not necessarily preferable (not so preferable).

The shape of the ceramic fiber is also not particularly limited. For example, short fibers having an average diameter of 3 to 10 μm and an average length of 0.2 to 100 mm, fiber bundles obtained by bundling hundreds to thousands of such short fibers, or continuous long fibers may be included. However, from the viewpoint of maintaining the porosity within the range of the present invention, the form in which the aforementioned short fibers are dispersed is preferable.

The addition rate of ceramic fibers is not particularly limited, but if it is too small, the effect of reducing the bulk specific gravity may hardly be obtained. In addition, if it is too large, the proportion of pores with a pore diameter of 0.01 μm or more to less than 0.8 μm and pores with a pore diameter of 0.8 μm or more and less than 10 μm in the whole will decrease, and thus the suppression of the increase in thermal conductivity described later may not be sufficiently obtained. Effect.

It should be noted that, in one solution of the present invention, if pores with a pore diameter of 0.8 μm or more and less than 10 μm account for more than 10 vol% and less than 40 vol% of the total pore volume, and pores with a pore diameter of 0.01 μm or more and less than 0.8 μm are in the If the total pore volume accounts for 5 vol% or more and 10 vol% or less, pores of 1000 μm or more may be included.

A preferable addition rate of the ceramic fiber is 0.05 vol% to 35 vol% with respect to the porous sintered body, more preferably 0.1 vol% to 30 vol%.

In addition, the content rate of a ceramic fiber is adjusted with the weight ratio of a ceramic fiber and solid content other than a ceramic fiber. In terms of the added amount, it is not less than 0.5 wt % and not more than 75 wt %, more preferably not less than 5 wt % and not more than 60 wt %.

In addition, the distribution of ceramic fibers in MgAl ₂ O ₄ can be timely adjusted according to the requirements of the designed thermal insulation material. As an example, if the density of the fibers is high in the surface layer and low in the center, the surface layer has high strength and can be made into a heat insulating material that is hard to deform.

The porosity of the porous sintered body in one aspect of the present invention is set to be 85 vol % or more and less than 91 vol %. When the porosity is lower than 85 vol %, the proportion of the base material composed of MgAl ₂ O ₄ in the porous sintered body is high, conduction heat transfer increases, and it may be difficult to make the thermal conductivity sufficiently small. On the other hand, when the porosity is 91% by volume or more, the proportion of the base material portion composed of MgAl ₂ O ₄ in the porous sintered body is absolutely low, so that it becomes extremely fragile, and sufficient strength cannot be obtained. heat resistance.

The said porosity is computed by JISR2614 "The measuring method of the specific gravity and true porosity of a refractory heat insulating brick".

In the pore structure of the porous sintered body, pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 10 vol% or more and 40 vol% or less of the total pore volume.

Most of the pores in the porous sintered body are small pores with a diameter of less than 10 μm. When there are many pores with a diameter of 10 μm or more, the infrared scattering effect becomes insufficient. Therefore, it is preferable to have at least one pore diameter distribution peak in the range of 0.8 μm to less than 10 μm in pore diameter.

In addition, if the proportion of pores with a pore diameter of 0.8 μm or more and less than 10 μm in the total pore volume is less than 10 vol%, the infrared scattering effect may become insufficient. On the other hand, when it exceeds 40 vol%, it becomes difficult to obtain a porosity of 85 vol% or more.

In addition, among the pores of the porous sintered body, pores (micro pores) having a pore diameter of 0.01 μm or more and less than 0.8 μm account for 5 vol% or more and 10 vol% or less of the total pore volume.

Such minute pores exist in the ratio as described above, thereby increasing the number of pores per unit volume, increasing the amount of phonon scattering at grain boundaries, and suppressing conduction heat transfer.

If the ratio of the microscopic pores to the total pore volume is less than 5 vol%, the number of pores per unit volume will be small, and the effect of suppressing conduction and heat transfer will become insufficient. On the other hand, when it exceeds 10 vol%, it becomes difficult to obtain a porosity of 85 vol% or more.

The porous sintered body may have a pore diameter distribution peak in a range of pore diameters exceeding 10 μm. However, coarse pores lead to a decrease in thermal insulation due to radiation heat transfer, and therefore, as an example, the presence of pores with a pore diameter exceeding 1000 μm is not preferable.

The pore size distribution in the porous sintered body can be measured in accordance with JIS R1655 "Test method for pore size distribution of molded body of fine ceramics by mercury porosimetry".

In addition, the bulk specific gravity of the heat insulating material related to one aspect of the present invention is 0.6 or less. Here, bulk specific gravity can be measured by JISR2614 "the specific gravity of a refractory heat insulating brick and the measuring method of a true porosity."

As mentioned above, ceramic fibers are contained in MgAl ₂ O ₄ , the porosity is 85 vol% or more and less than 91 vol%, and the pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 10 vol% or more and 40 vol% or less of the total pore volume, Pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for 5 vol% or more and 10 vol% or less of the total pore volume. In such a pore form, ceramic fibers can be included, thereby reducing the strength without reducing the weight. Reduce bulk specific gravity.

In addition, the thermal conductivity of the heat insulating material is preferably not more than 1.5 times the thermal conductivity at 1000°C to 1500°C and not more than 1.5 times the thermal conductivity at 20°C to less than 1000°C.

The thermal insulating material whose thermal conductivity is suppressed in the high temperature range can maintain the same thermal insulation effect in the high temperature range of 1000°C or higher as that in the low temperature range of less than 1000°C.

The thermal conductivity of the heat insulating material in the high temperature range of 1000°C to 1500°C is 0.45W/(m·K) or less, specifically 0.40W/(m·K) or less. In this way, the heat insulating material whose thermal conductivity is suppressed without increasing even in the high temperature range of 1000°C or higher has little variation in the heat insulating effect even when used in the high temperature range.

Here, the bulk specific gravity range of 0.6 or less is not necessarily a lightweight type as a porous sintered body, but it is light enough as a heat insulating material having the above-mentioned effect of suppressing the increase in thermal conductivity of the present invention. It can be said that it is advantageous in that the strength can be ensured by making the bulk specific gravity moderate, and it is difficult to be damaged, so it is easy to handle. The lower limit of the bulk specific gravity is not particularly limited, as long as it is within a range that can be used practically as a heat insulating material, and may be 0.3 or more as an example.

Next, a heat insulating material according to another aspect of the present invention will be described. The heat insulating material involved in another aspect of the present invention includes a porous sintered body with a porosity of 70 vol% or more and less than 85 vol%, and pores with a pore diameter of 0.8 μm or more and less than 10 μm account for 40 vol% or more and less than 40 vol% of the total pore volume. 70vol%, and pores with a diameter of 0.01 μm or more and less than 0.8 μm account for more than 10vol% and less than 30vol% of the total pore volume, and the porous sintered body is formed of MgAl ₂ O ₄ (spinel) raw materials and ceramic fibers (contains ceramic fibers in MgAl ₂ O ₄ ), the thermal conductivity above 1000°C and below 1500°C is not more than 1.5 times the thermal conductivity above 20°C and below 1000°C.

The difference from the heat insulating material involved in one solution of the present invention is: porosity, the volume ratio of pores with a diameter of 0.8 μm or more and less than 10 μm, and pores with a diameter of 0.01 μm or more and less than 0.8 μm in the total pores. Therefore, since the porosity is lower than that of the heat insulating material according to one aspect of the present invention, the bulk specific gravity is slightly increased, but the thermal conductivity can be suppressed even lower.

In particular, this can be said to be the effect of increasing the ratio of pores with a diameter of 0.8 μm to less than 10 μm and pores with a diameter of 0.01 μm to less than 0.8 μm compared with the solution of the present invention.

It should be noted that for the heat insulating material involved in the above another solution, the thermal conductivity at temperatures above 1000°C and below 1500°C is 0.40W/(m·K) or less, preferably 0.35W/(m·K) )the following. Alternatively, it is more preferable if the thermal conductivity at 1000°C to 1500°C is not more than 1.2 times the thermal conductivity at 20°C to less than 1000°C.

As described above, the heat insulating material related to the present invention is that by adding ceramic fibers to MgAl ₂ O ₄ and further controlling the ratio of the porosity and the pore diameter in a predetermined range appropriately, the thermal conductivity suppression effect and weight reduction can be achieved. Thermal insulation materials that coexist in any balance.

Therefore, compared with conventional heat insulating materials composed of a single component of MgAl ₂ O ₄ , material design can be performed for the purpose of improving predetermined characteristics, and a wider range of requirements can be met.

In addition, the manufacturing method of the heat insulating material concerning this invention mentioned above is not specifically limited, The manufacturing method of a well-known porous sintered body can be used. For example, the formation and adjustment of the pore structure can be performed by adding a pore-forming material and a foaming agent.

In addition, the heat insulating material according to the present invention can have various modifications as long as there is no adverse effect such as significantly deteriorating the heat insulating properties. For example, fibers made of various materials may also be added. In addition, fine particles may be further added. Alternatively, a fiber-free region may be partially set. Furthermore, various films may be provided on the surface layer of the heat insulating material according to the present invention to further improve heat resistance.

Example

The present invention will be specifically described below based on examples, but the present invention is not limited by the examples shown below.

(Examples 1-3, Reference Examples 1 and 2, and Comparative Examples 1-3)

With respect to 11 mol of hydraulic alumina powder (BK-112; manufactured by Sumitomo Chemical Co., Ltd.), magnesium oxide powder (MGO11PB; manufactured by High Purity Chemical Laboratory Co., Ltd.) was mixed in a ratio of 9 mol, and the amount of hydraulic alumina and The total weight of magnesium oxide is equal to the weight of pure water, so that it is uniformly dispersed to prepare a slurry. Next, prepare bulk alumina fibers with an average diameter of 3 to 5 μm and an average length of 100 mm or less, and granular acrylic resin with a diameter of 5 to 10 μm as a pore-forming material, and appropriately change the addition rate of the alumina fibers and the diameter of the pore-forming material. and the addition amount, calcination temperature and calcination time, the porous sintered body having the pore structure respectively shown in Examples 1-3, Reference Examples 1 and 2, and Comparative Examples 3-5 in Table 1 below was produced. In addition, the pore-forming material is added in the range of 40 to 70 vol% relative to the slurry, and the alumina fiber is added and mixed in the amount shown in Table 1. After molding to obtain a molded body of 60 mm × 70 mm × 20 mm, they are placed in the atmosphere. In 1500 ℃ ~ 1600 ℃, change in the range of 3 ~ 4 hours and bake to produce a porous sintered body.

The porous sintered body obtained above was subjected to X-ray diffraction (X-ray diffraction device: RINT2500 manufactured by Rigaku Co., Ltd., X-ray source: CuKα, voltage: 40kV, current: 0.3A, scanning speed: 0.06°/s) The crystalline phase was identified, and a magnesia spinel phase was observed.

For the above-mentioned Examples 1-3, Reference Examples 1 and 2, and Comparative Examples 1-3, the porosity and bulk specific gravity (bulk density) were measured referring to JIS R2614 "Measurement method of specific gravity and true porosity of refractory and heat-insulating bricks". The results are shown in Table 1.

In addition, for the above-mentioned Examples 1 to 3, Reference Examples 1 and 2, and Comparative Examples 1 to 3, the pore volume was measured using a mercury porosimeter (AutoPore IV9500 manufactured by Shimadzu Corporation). In FIG. 1 , the pore diameter distributions of Examples 1 to 3 and Reference Example 1 are shown as examples. Based on this pore diameter distribution, the volume ratio (vol%) of the volume of pores with a pore diameter of 0.8 μm to less than 10 μm and the volume of pores with a pore diameter of 0.01 μm to less than 0.8 μm is calculated relative to the total pore volume.

In addition, in the above-mentioned Examples 1 to 3, Reference Examples 1 and 2, and Comparative Examples 1 to 3, the weight ratio of Si to Mg in the sintered body is such that the porous sintered body Calculated by pulverizing and measuring with fluorescent X-rays.

In addition, about the above-mentioned Examples 1-3, Reference Examples 1, 2, and Comparative Examples 1-3, referring to JISR2616, the thermal conductivity up to 1500 degreeC was measured by the hot wire method.

In addition, the reheating shrinkage was measured after maintaining at 1600 degreeC for 12 hours and cooling, referring JISR2613. Similarly, it maintained at 1700 degreeC for 12 hours, and measured after cooling. In addition, the pore size distribution of Example 1A obtained by heat-treating Example 1 at 1700° C. for 12 hours is shown in FIG. 2 . Similarly, the pore size distribution of Example 2A obtained by heat treatment of Example 2 at 1700°C for 12 hours is shown in Figure 2.

In addition, regarding the spalling resistance, referring to JIS R2657, it was carried out at a test temperature of 1000°C by the air cooling method, and the state of the heating surface was studied.

The above various evaluation results are shown in Table 1 below.

As shown in Examples 1 to 3 and Reference Rates 1 and 2 in Table 1, when the weight ratio of Si to Mg in the sintered body is 0.15 or less, the reheat shrinkage at 1600°C is 2% or less , can obtain low thermal conductivity, good heat resistance. In addition, as shown in Example 2 and Reference Example 1, when the weight ratio of Si to Mg in the sintered body is less than 0.0001, the reheating shrinkage at 1700°C is 1.3% or less, and more Low thermal conductivity, better heat resistance.

It should be noted that, compared with Examples 1 to 3, Reference Examples 1 and 2, in which the amount of added fiber was small, was inferior in terms of the reduction in spalling resistance, which was considered to be caused by the insufficient amount of fiber. In addition, Comparative Examples 1 to 3 in which at least any one of porosity, fiber addition amount, and Si/Mg deviated from the ranges of the present invention, compared with Examples 1 to 3 or Reference Examples 1 and 2, had lower thermal conductivity. In any one of the results of rate and reheat shrinkage, it appears inferior.

(Examples 4-6, Comparative Examples 4-6)

With respect to 11 mol of hydraulic alumina powder (BK-112; manufactured by Sumitomo Chemical Co., Ltd.), magnesium oxide powder (MGO11PB; manufactured by High Purity Chemical Laboratory Co., Ltd.) was mixed at a ratio of 9 mol, and hydraulic alumina powder was added to it. The total weight of magnesia and magnesia is equal to the weight of pure water, so that it is uniformly dispersed to prepare a slurry. Then, by changing the diameter and addition amount of the pore-forming material (granular acrylic resin with a diameter of 5 to 10 μm), and firing at a fixed firing temperature for 3 hours at 1500° C., Examples 4 to 6 and Comparative Examples with the following Table 2 were produced. Each porous sintered body constituted by pores shown in 4 to 6, respectively. Next, as the fibrous layer, alumina fibers with an average diameter of 3 to 5 μm and loose fibers with an average length of 100 mm or less were used, and the two fibers shown in Examples 4 to 6 and Comparative Examples 4 and 6 in Table 2 below were mixed. Alumina fiber with a weight ratio of silicon oxide, which is coated on one main surface of each porous sintered body with a thickness of 5mm to form a fibrous layer, and then fixed at a firing temperature of 1500 ° C for 3 hours to obtain a 25mm * 50mm * 200mm the roasted body. In addition, one main surface on which the fibrous layer was formed was any one of the 50 mm×200 mm planes, and there was no fibrous layer in Comparative Example 5. As described above, evaluation samples of heat insulating materials shown in Examples 4 to 6 and Comparative Examples 4 to 6 in Table 2, respectively, were produced.

For each porous sintered body obtained above, X-ray diffraction (X-ray diffraction device: RINT2500 manufactured by Rigaku Co., Ltd., X-ray source: CuKα, voltage: 40kV, current: 0.3A, scanning speed: 0.06°/s) The crystalline phase was identified, and a magnesia spinel phase was observed.

For Examples 4 to 6 and Comparative Examples 4 to 6, the porosity, pore volume ratio, and thermal conductivity were measured or calculated, respectively, and the above various evaluation results are summarized and shown in Table 2 below. In addition, the porosity and pore volume ratio were evaluated for the porous sintered body, the silica content was evaluated for the fibrous layer, and the thermal conductivity and handleability were evaluated for the heat insulating material.

Based on the above method, the pore volume was measured using a mercury porosimeter (AutoPore IV9500 manufactured by Shimadzu Corporation). Referring to JISA1412-2, thermal conductivity was evaluated. The operability was evaluated by grasping and holding it horizontally at a distance of 50 mm from the end point on the 200 mm long side of a 25 mm × 50 mm × 200 mm calcined body, judging by the state of shape retention at this time, and 〇 indicates that the shape is maintained The sintered body with × represents the broken sintered body.

[Table 2]

From the evaluation results shown in Table 2, it is known that the thermal conductivity at 1000° C. or higher is suppressed to be low within the practical range of the present invention. Compared with Comparative Example 5, which is a porous sintered body without a fibrous layer, it was found that the workability was also increased and the toughness was improved.

On the other hand, in Comparative Example 4, the porosity was low and the silica component in the fiber was large compared with the practice range of the present invention, so the thermal conductivity tended to be high.

In addition, as shown in Comparative Example 5, it can be said that only the porous layer has poor handleability and poor toughness.

Also, as shown in Comparative Example 6, when fibers with a silica content exceeding 55 wt % were used, peeling occurred between the porous layer and the fibrous layer. Therefore, measurement of thermal conductivity and operability could not be performed.

Although the porous sintered body is spinel formed of MgAl ₂ O ₄ in the above examples, as described above, in the present invention, ZnAl ₂ O ₄ , FeAl ₂ O ₄ , NiAl ₂ O ₄ , MnAl ₂ Any spinel in O ₄ can also achieve the same effect. They sequentially use porous ceramic raw materials obtained by combining ZnO _{+ Al2O3} , _{Fe2O3 + Al2O3} , NiO _{+ Al2O3} , _{MnO + Al2O3} , and can be made in the same manner as the above _- mentioned _MgAl2O4 except that manufacture.

(Examples 7-9, Comparative Example 7)

With respect to 11 mol of hydraulic alumina powder (BK-112; manufactured by Sumitomo Chemical Co., Ltd.), magnesium oxide powder (MGO11PB; manufactured by High Purity Chemical Laboratory Co., Ltd.) was mixed at a ratio of 9 mol, and hydraulic alumina powder was added to it. The total weight of magnesia and magnesia is equal to the weight of pure water, so that it is uniformly dispersed to prepare a slurry. Next, prepare loose alumina fibers with an average diameter of 3 to 5 μm and an average length of 100 mm or less, and granular acrylic resin with a diameter of 5 to 10 μm as a pore-forming material, and appropriately change the addition rate of the alumina fibers and the diameter of the pore-forming material. and the addition amount, calcination temperature and calcination time, the porous sintered body having the pore structure respectively shown in Examples 7 to 9 and Comparative Example 7 in Table 3 below was produced. In addition, the pore-forming material is added in the range of 40-70vol% relative to the aforementioned slurry, and the alumina fiber is added in the range of 50wt%. After mixing and molding to obtain a molded body of 60mm×70mm×20mm, it is placed in the atmosphere at 1500°C to 1600°C. ℃, within the range of 3 to 4 hours, and fired to produce a porous sintered body.

For each porous sintered body obtained above, X-ray diffraction (X-ray diffraction device: RINT2500 manufactured by Rigaku Co., Ltd., X-ray source: CuKα, voltage: 40kV, current: 0.3A, scanning speed: 0.06°/s) The crystalline phase was identified, and a magnesia spinel phase was observed.

(reference example 3)

A commercially available fiber heat insulating material (heat-resistant temperature: 1600° C.) was used as Reference Example 3.

For Examples 7 to 9, Comparative Example 7, and Reference Example 3, the pore volume was measured using a mercury porosimeter (AutoPore IV9500 manufactured by Shimadzu Corporation). Its pore size distribution is shown in FIG. 5 . The bulk specific gravity was measured with reference to JIS R2614 "Measurement method of specific gravity and true porosity of refractory and heat insulating bricks". In addition, thermal conductivity was measured with reference to JISR2616 about each porous sintered body or heat insulating brick of the said Example and the comparative example. The fiber content (vol%) of the calcined body was calculated from the area occupied by the fibers in the observation field after cleaving an arbitrary cross-section of each porous sintered body and observing it under a microscope. The determination of the fracture energy value is to make the sample fail stably under the condition of a certain displacement speed of the load point, and divide the work equivalent to the area enclosed by the load-displacement curve and the displacement axis by the value measured by a universal projector, etc. Calculated by twice the projected fracture area A. These various evaluation results are summarized in FIG. 4 and Table 3 below.

From the evaluation results shown in Table 3, it can be seen that in Examples 7 to 9 in which the ratio of the fiber added and the pore volume is within the implementation range related to one aspect of the present invention, the thermal conductivity at 1000°C to 1500°C It is lower than 0.40W/(m?K), and the bulk specific gravity is also lower than 0.6.

In contrast, in Comparative Example 7 not containing fibers, the bulk specific gravity was higher than 0.6.

(Examples 10-13, Comparative Example 8)

The addition rate of alumina fibers, the diameter and addition amount of pore-forming materials, the firing temperature and the firing time were appropriately changed, and in addition, Examples 10-13 having the following Table 4 were produced and evaluated in the same manner as Examples 7-9, and compared Porous sintered bodies each having the pores shown in Example 8.

From the evaluation results shown in Fig. 5 and Table 4, it can be seen that in Examples 10 to 13 in which the ratio of porosity and pore volume is within the practice range according to another aspect of the present invention by adding fibers, at 1000° C. A thermal conductivity of ~1500°C is sufficiently low.

Furthermore, in Examples 12 to 13, the thermal conductivity at 1000°C to 1500°C is lower and more preferable.

On the other hand, in Comparative Example 8, in which the ratio of porosity and pore volume is outside the implementation range according to another aspect of the present invention, the thermal conductivity from 1000°C to 1500°C is slightly higher.

It should be noted that Reference Example 3 is a heat insulating material composed only of fibers. Compared with the product of the present invention, the value of bulk specific gravity is much lower. However, the thermal conductivity at 1000°C to 1500°C in Examples is 0.51W/(m·K).

From this, it can be said that the heat insulating material according to the present invention is particularly preferable for applications where low thermal conductivity in a high temperature range and characteristics of suppressing an increase in thermal conductivity are emphasized.

In addition, for Examples 7 to 13 and Comparative Examples 7 and 8, the value of breaking energy was measured and compared. The determination of the fracture energy value is to make the sample fail stably under the condition of a certain displacement speed of the load point, and divide the work equivalent to the area enclosed by the load-displacement curve and the displacement axis by the value measured by a universal projector, etc. Calculated by twice the projected fracture area A.

Result, embodiment 7 is 8.8N/m, embodiment 8 is 10.5N/m, embodiment 3 is 17.3N/m, embodiment 10 is 4.7N/m, embodiment 11 is 5.2N/m, embodiment 12 It is 1.7N/m, and Example 13 is 4.3N/m. In contrast, in Comparative Example 7, it was 0.5 N/m, and in Comparative Example 8, it was 8.7 N/m.

From the above results, compared with Comparative Example 7 in which no fiber was added, the energy-to-break values were higher in Examples 7 to 13 to which fibers were added according to the present invention. In addition, in Comparative Example 8, which exceeds the practical range of the porous sintered body according to another aspect of the present invention, that is, the porosity of 85 vol%, the increase in thermal conductivity at 1000° C. to 1500° C. is higher than that of Examples 10 to 13. It can be said that the effect of the present invention of excellent thermal insulation at high temperature cannot be sufficiently obtained.

It should be noted that although alumina fibers were exemplified as the added fibers in the above-mentioned examples, if silica is included in the fibers used in the present invention, the heat resistance and heat insulation properties of the porous sintered body as a whole will be reduced. decline. Not limited to alumina fibers, when other types of fibers are used, it is also preferable that the silica content in the fibers is 5 wt% or less. Thereby, shrinkage can be suppressed not only when producing a porous sintered body but also during use at high temperature, and the target pore size distribution can be maintained. That is, by using fibers with a silica content of 5 wt % or less, a porous sintered body excellent in heat resistance and heat insulation can be obtained.

Claims (11)

1. A heat insulating material comprising a porous sintered body having a porosity of 70 vol% or more and less than 91 vol%; The pores with a pore diameter of 0.8 μm or more and less than 10 μm account for more than 10 vol% and less than 70 vol% of the total pore volume, and the pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for more than 5 vol% and less than 30 vol% of the total pore volume, The porous sintered body is a sintered body formed of a MgAl ₂ O ₄ (spinel) raw material and fibers formed of an inorganic material, The thermal conductivity at 1000°C to 1500°C is 0.40W/(m?K) or less, The weight ratio of Si to Mg in the porous sintered body is 0.15 or less. 2. The heat insulating material according to claim 1, wherein the weight ratio of the Si to the Mg in the porous sintered body is 0.0001 or less. 3. The heat insulating material according to claim 1 or 2, characterized in that, The porosity is more than 85vol% and less than 91vol%, The pores with a pore diameter of 0.8 μm or more and less than 10 μm account for more than 10 vol% and less than 40 vol% of the total pore volume, and the pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for more than 5 vol% and less than 10 vol% of the total pore volume. 4. The heat insulating material according to claim 1 or 2, characterized in that, The porosity is more than 70vol% and less than 85vol%, The pores with a pore diameter of 0.8 μm or more and less than 10 μm account for more than 40 vol% and less than 70 vol% of the total pore volume, and the pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for more than 10 vol% and less than 30 vol% of the total pore volume. 5. The heat insulating material according to claim 1, wherein the inorganic material is a ceramic reinforcement material. 6. The thermal insulation material of claim 5, wherein the ceramic reinforcing material is ceramic fiber. 7. A method for producing a heat insulating material, which is the method for producing a heat insulating material according to claim 5 or 6, characterized in that it includes the step of adding a ceramic reinforcing material with a silicon dioxide content of 5 wt% or less, the ceramic reinforcing material The material is added in an amount of 0.5 wt% or more and less than 60 wt% of the porous sintered body. 8. A heat insulating material comprising a porous sintered body having a porosity of 70% or more, characterized in that, The porous sintered body includes a spinel sintered body made of MgAl ₂ O ₄ (spinel) and a fibrous layer existing on at least one surface of the spinel sintered body Raw material is formed, the fibrous layer is formed from fibers formed from inorganic materials, Pores with a pore diameter of more than 1000 μm account for 10 vol% or less of the total pores of the porous sintered body, The pores with a pore diameter of 0.8 μm or more and less than 10 μm account for more than 50 vol% and 80 vol% of the pores with a pore diameter of 1000 μm or less, and the pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for more than 10 vol% of the pores with a pore diameter of 1000 μm or less. Below 30vol%, The silicon dioxide component in the fibers of the fibrous layer is 55 wt% or less, The thermal conductivity at 1000° C. to 1500° C. is 0.40 W/(m·K) or less. 9. A heat insulating material comprising a porous sintered body with a porosity of 85 vol% or more and less than 91 vol%; The pores with a pore diameter of 0.8 μm or more and less than 10 μm account for more than 10 vol% and less than 40 vol% of the total pore volume, and the pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for more than 5 vol% and less than 10 vol% of the total pore volume, The porous sintered body is formed from MgAl ₂ O ₄ (spinel) raw material and ceramic fibers, The thermal conductivity at 1000°C to 1500°C is 0.40W/(m?K) or less, The bulk specific gravity is 0.6 or less. 10. The heat insulating material according to claim 9, wherein the thermal conductivity at 1000°C to 1500°C is not more than 1.5 times the thermal conductivity at 20°C to 1000°C. 11. A heat insulating material comprising a porous sintered body having a porosity of 70 vol% or more and less than 85 vol%; Stomata with a pore diameter of 0.8 μm or more and less than 10 μm account for more than 40 vol% and less than 70 vol% of the total pore volume, and pores with a pore diameter of 0.01 μm or more and less than 0.8 μm account for more than 10 vol% and less than 30 vol% of the total pore volume %, The porous sintered body is formed from MgAl ₂ O ₄ (spinel) raw material and ceramic fibers, The thermal conductivity at 1000°C or more and 1500°C or less is not more than 1.5 times the thermal conductivity at 20°C or more and less than 1000°C.